Kellerman's psychologist/sleuth Alex Delaware nimbly executes tricky steps of his own when called in to consult on the mysterious ailments afflicting a baby being seen at his training hospital in Los Angeles. In his seventh appearance (after Private Eyes ), Delaware is in top form, carefully pursuing the possibility that 21-month-old Cassie Jones may be the victim of Munchausen's Disease by Proxy, a complex syndrome in which a parent, usually the mother, secretly causes the symptoms that endanger the child. That Cassie is the only grandchild of the hospital's new CEO, a corporate hotshot who has demoralized the staff with cutbacks and a new administration of ``paramilitary types,'' adds political twists to the case's knotty psychological aspects. After a doctor involved in computer research is murdered in the hospital parking lot, Delaware calls on his friend Milo, a gay LAPD homicide cop currently serving as an input clerk. They link an earlier murder to the hospital and then key into a secret federal investigation, all the while trying to keep Cassie safe. With familiar characters, including Delaware's woodworking girlfriend Robin, and some well-developed new ones, notably the hospital's thuggish security head and an uptight pediatric nurse, Kellerman steadily turns up the suspense, reserving some surprises to spring near the end of this intricate tale, the best of recent Alex Delaware stories. (Jan.)